White Paper
The Drive to Go from Wired to Wireless Sensors
Learn more about the four main drivers in the condition monitoring industry that have been pushing the need for sensors to go from wired to wireless.
Condition-based monitoring of rotating equipment assets is a proven method of managing plant reliability and safety that has been practiced for decades. Vibration monitoring is a dominant portion of that. Traditionally, vibration sensors have been installed on the machine, and hard-wired back to a central machinery protection system (e.g. vibration monitor). While reliable, this technique is expensive and therefore usually reserved for large rotating machines; typically steam-driven turbines or large combustion (gas) turbines, deemed “critical” to the plant’s operation.
For less critical assets (the so-called balance-of-plant machines), such as centrifugal pumps and compressors, the business case for installing such a condition monitoring system is less clear, or even untenable. The loss of availability of such machines, however, are in some cases no less important to the safe, reliable operation of a plant. There still exists, then, a need to economically condition monitor balance-of-plant machines.
As a solution, wireless vibration sensors have been proposed for over a decade. Many commercial implementations have met with mixed results, for a number of reasons. TE Connectivity (TE) feels that technology and market forces have converged sufficiently, however, to introduce such a wireless sensor.
Industry Drivers
We see at least four drivers shaping this market space:
- Driver 1: Ever-increasing demand for data by plant operators at an economical price
- Driver 2: Continued electrification has dramatically improved battery performance
- Driver 3: The rise of the Internet of Things (IoT) has improved digital radio performance
- Driver 4: Edge computing in IoT devices further enhances wireless communications
Driver 1
Ever-increasing demand for data by plant operators at an economical price
As the march towards digitization continues unabated, one lesson that becomes clear is that the demand for data is never satisfied. Supplying this data, however, must be done economically. Condition monitoring of plant assets is no different.
Conventional installations require a multi-conductor, shielded cable to be connected to the sensor installed on the machine and run all the way back to a central machinery protection system. The total cable run length could be hundreds of feet long. Every sensor requires this. With multiple sensors, thousands of feet of cable are required. Further, to meet National Electrical Code® and local plant requirements, typically the first tens of feet of cable from the sensor at the machine is required to be installed in conduit. The remaining length back to the central station is often bundled in larger conduits or cable trays. All of this adds up to expensive labor and materials and it is not easily scalable.
Wireless sensors solve this problem. The wireless gateway is hard-wired back to a central station. But many wireless sensors are handled by a single gateway, thus eliminating the cable and conduit from the machine. Now the single cable from the gateway back to the central station is carrying data from many sensors, not just one. This is an easily scalable architecture, as the gateway can likely handle additional wireless sensors, or an additional gateway could be installed to accommodate an additional double or triple the number of sensors – a task that would be impossible to do the conventional way at the same cost.
Driver 2
Continued electrification has dramatically improved battery performance
Wireless sensors obviously require batteries to perform as expected. The most significant factor in the success or failure of utilizing wireless sensors is the battery’s performance. Having to frequently replace depleted batteries chips away at the economic business case for using wireless sensors, not to mention loss of data while the sensor is left unpowered.
Technological improvements in battery performance have not kept up with other performance improvements in electronics, until recently. The drive for electrification in the transportation sectors (electric vehicles) and aerial drones has dramatically lowered the cost of batteries and improved their performance. Lithium based batteries, still the best technology and preferred choice for wireless applications, has come down in price significantly, from about $1,200 per kWh in 2010 to about $175 per kWh in 2018. The day is not far off when operating an electric vehicle will be cheaper than operating a gas-powered vehicle. Availability of improved battery life makes operation of wireless sensors feasible economically. Going from replacing batteries every few months, to every year, to every two years and beyond suddenly makes operation of wireless sensors cost competitive with wired sensors.
Driver 3
The rise of the Internet of Things (IoT) has improved digital radio performance
Connecting devices to the internet so that they can be controlled and managed
remotely has dramatically driven improvements in digital radio communications, both the radio hardware and communications protocols. With the rise of smart phones and always-connected tablets and PCs, radio hardware costs have been driven continuously downward. Mobility requirements have demanded ultra-low power radio chipsets to extend battery life. The sheer volume of data generated from all these devices has demanded efficient, economical use of wireless bandwidth.
LoRaWANTM and Bluetooth Low Energy (BLE) radio communication methods have emerged as the most promising of the lower power wide are networks (LPWAN) available.
LoRaWANTM benefits:
- Sub-gigahertz unlicensed radio spectrum
- Ultra low power to extend battery life
- Long range capabilities between the sensor and the gateway (5 km or greater, depending on local conditions)
- Flexible deployment and ability to penetrate deep in mixed environments
- Allows data to be sent asynchronously when needed, further extending battery life.
BLE benefits:
- Global 2.4 GHz unlicensed radio spectrum
- Ultra-low power that extends battery life
- Easy communication due to large installment base of gateways, smartphones, and tablets
- Larger data bandwidth to allow raw data transfer for analysis
- Allows data sent in broadcast mode, allowing easy connection and further extending battery life.
Driver 4
Edge computing in IoT devices further enhances wireless communication
Many years ago, Gordon Moore famously predicted that performance in digital devices would double approximately every 18 months (known as Moore’s Law). This prediction has generally held true, to the point where there is now tremendous computing power in the palm of your hand, or in your wearable device (e.g. smart watch). This has enabled Edge computing; the ability to process data at or near the end of the network (the “edge” of the network), rather than send that data in raw form all the way back to a central station to be processed there.
For a wireless vibration sensor, a perhaps obvious application of Edge computing is calculating the FFT (Fast Fourier Transform) of a sampled vibration waveform at the sensor itself. In a conventional system, the raw vibration waveform would be sent to the central station (as an analog signal) and the FFT calculated there. With Edge computing, the FFT can be calculated in the sensor and the processed data sent back. Rather than sending back raw vibration signals, this reduces bandwidth overhead and usage of battery power. But this is only a simple example. Ultimately much more computing could be done at the sensor. Given the appropriate algorithms, the sensor could “learn” about the machine it is installed on and when it is running well and when it is not. The building blocks are in place for a truly smart condition-monitoring vibration sensor.
Conclusion
With these market drivers at play, TE Connectivity has designed the 89xxN and 85xxN wireless vibration sensors. Our new sensors satisfy the demand from plant operators for machine condition data, with an easily scalable wireless architecture. The 89xxN has a built-in LoRa™ radio and uses the LoRaWANTM protocol to communicate back to a wireless gateway. It can achieve up to a 4-year battery life depending on the sampling rate. The 89xxN also supports BLE connections for device configuration, or a user can leverage the TE Toolbox to configure the sensor over the LoRaWAN network. The 85xxN is designed entirely around BLE for both data transmission and configuration. Supporting the latest Bluetooth 5.0 standards you can ensure this sensor will work flawlessly with gateways, smartphones, or tablets. To cover all ranges of machines and conditions. The 8xx1N platform was designed with flexibility in mind. The 8911N or 8511N is designed for simpler single machine analysis using a single axis accelerometer. For more complex machine analysis there is the 8931N or 8531N which utilizes a tri-axial accelerometer. The 89x1N or 85x1N can be installed in a complex plant environment due to the water and dust proof design and Hazardous location certifications.
The 89xxN or 85xxN wireless vibration sensors are the condition-monitoring sensors you need for your 21st century plant.
LoRaWAN is a trademark.
